Safety-valve



e. H. CL'AR K. SAFETY VALVE. v APPLICATION FILEDDCT- 23. 19I9.

Big. 1.

w Q 11111 amrn Pafientgd M 6, 1920.

UNITED STATES GEORGE HALL CLARK, or cAME mGE, MASsAcriUsETTs, AssIG oE. 'To CROSBY STEAM GAGE & VALVE ooMr NY, F BOSTON, MASSACHUSETTS, A CORPORA- TION 0E MAssAcHqsETTs.

To all whom it may concern:

Be it knoyvn that I, GEORGE HALL CLARK, a citizen of the United States of America and resident of Cambridge, in the county of Middlesex and State of Massachusetts, have invented new and useful Improvements in Safety-Valves, of which the following is a specification.

My invention relates to safety valves for steam boilers, and consists'in improvements applicable to safety valves of the prevalent huddling chamber type, such as the commercially known Crosby standard stationary valve. The object of my invention is to in-- crease the maximum lift of such a valve, without sensibly affecting the behavior of the valve at low values of lift, either when opening or closing.

In the drawings hereto annexed which illustrate my invention and show an example thereof,-

Figure 1 is a vertical cross section of a safety valve showing its well known characteristic parts; and I Fig. 2 is a fragmentary side elevation of that portion of the valve structure which contains the member chiefly characteristic of my improvement.

In the drawing the following named parts are comprised in a safety valve of the general character indicated A is the valve disk, -B the base on which is formed valve seat S. The valve disk and base are shaped to form the annular pressure chamberor huddling chamber D which lies between the seat S.

and the lip a. The flange K provided with a series of apertures F- terminates in a lip f between which and'the lip a is located the lip apertureE, which is slightly open" when the disk A is seated at S. The adjusting ring 0 is adjustably mounted onthebase B immediately below the flange K and cooperates in the well known manner with the apertures F to control the blowdown of the" "alve.

n The well-known action of'safety valves of. this type is as follows: When pressure in. the boiler-reaches the point at which the "alve is set, the disk A lifts slightly, steam passes through the seat aperture thus produced into the chamber D from which there are twooutlets, one through the lip aperture PAjTENT-OFFlCE. A

sAEETY-vALvE.

Specification of Letters Patent. Patented 1; 26 1920 Application filed October 23, 1919f Serial No. $3 2,749.

' E and the other downwardly, through the holes F and then outward over the ring C.

The aggregate of thareas of the lip aperture E and that over the ring C is such that pressure is built up in the chamber D and the valve pops, receiving a sudden, relatively large increase in lift. The extent of thislift ,depends'on the total upward pressure on the disk including the area in the chamber D and tlfe downward force exerted by the spring. Assuming'the. valve to be blowlng freely and to be of suflioient size to reduce the boiler pressure gradually, the

equilib ium is disturbed as pressure 1s reduced and the lift decreases. The discharge area at the seat S which may be termed the seat vent is directly proportional to the lift, while the discharge area from the chamber D is the aggregate of the area of openings from the chamber D when the valve is closed and the incrementin area brought about byv each increase in lift.

As the lip diameter is greater than the seat diameter the total effective area at the lip increases faster per unit of lift than the total area at. the seat. In short, the lip vent is initially larger than and increases faster than the seat vent. As the valve disk the ratio 5 is decreasing very rapidly. This ratio is the factor which determines the pressure in. the chamber D and the consequent lifting force on the disk. For this reason I provide means to make this factor or ratio approach more nearly to unity at V the higher lifts so that the valve may experience consequently an increase in lift and capacity. But it must be borne in mind that conditions at the lower lifts must be left undisturbed go that the designed factors for controlling the valve at those values of lift may not be appreciably altered.

In order to obtain increased lifts at the vide means by which in effect the outlet area at the lip or lip vent is made to approximate progressively to equality to the outlet area at the seat, leaving the controllin conditions unchanged at low lifts. 1

Heturning now. to the drawing: I attachto or form integrally with the adjusting ring C an annular screen G which lies around the valvedisk adjacent to the \lip vent. This screen is perforated with a number of circular apertures H which are so proportioned and positioned that at low lifts there is ample passage for'steam escaping from the lip vent at E; that is to say, at low lifts substantially none of the solid screen material is opposed to the free discharge of steam. But as the disk A lifts higher and the disk lip a rises, it comes into opposition to greater and greater extent with the solid material of which the screen G is composed; or speaking conversely, the width of the apertures H measured along horizontal chords becomes less and less.

This progressive opposition of more and more screen area to the discharge of the steam as the valve lifts, obstructs the efilux of steam, and has substantially the same effect as would be produced by an actual constriction of the vent area E.. This results in effect in makingthe area ratio Q approach unity at the higher lifts. Relatively to the lip vent the area of the series of holes H decreases progressively as the lift increases, but this area is sufficiently large and The result of employment of this improvement' is to increase the maximum lift of a valve from its original value by from fifty to seventy-five per cent.

I claim: I

1. In a safety valve of the character described, the combination of a valve disk and a base arranged, to provide a lip-vent between them, and means to obstruct the lipvent at relatively high valve lift-positions. ,2. Ina safety valve of the character described, the combination of a valve disk and a base arranged toprovide a lip-vent between them, and means to obstruct progressively the lip-vent at relatively high valve lift-positions. 1

. 3. In a'safety valve of the character described, the combination of a valve disk and a base arranged to provide a lip-vent between them, and a screen adjacent to the lip-vent and disposed to obstruct the same at relatively high valve-lift positions. i

4. In a safety valve of the character described, the combination -of a valve disk and a base arranged to providea lip-vent be- .tWeen'" them, and a screen adjacent to the lipvent and disposed'to obstruct the same progressively at relatively high valve-lift positlons.

scribed, the combination of a valve disk and a base arranged to provide a lip-vent between them,an adjusting ring, and a screen carried on the ring, adjacent to the lip-vent and disposed to obstruct the same at relatively high valve-lift "positions.

6. In a safety valve of the character de scribed, thecombination of a valve disk and a base arranged to provlde a, lip-vent be-.

tween them, an adjusting ring, and a screen carried on the ring, adjacent to the lip-vent and disposed to obstruct the same progressively at relatively high valve-lift positions.

7. In a safety valve of the character described, the combination of a valve disk and a base arranged to provide a lip-vent between them, an adjusting ring, and'an apertured screen carried on the ring, adjacent to the lip vent and disposed to obstruct the same at relatively high lift positions, the free area of the screen apertures being in the aggregate greater than the seat vent area at the maximum, of the latter.

.Signed by me at Boston, Massachusetts, this 21st day of October, 1919.

.GEORGE HALL CLARK 5. Ina safety valve of the character de- 

